merge-json-webpack-plugin

merge-json-webpack-plugin

Webpack plugin to merge multiple json files into one

Getting Started

Installation

npm i -D merge-json-webpack-plugin
# or
yarn add --dev merge-json-webpack-plugin

Usage

// webpack.config.js
const MergeJsonPlugin = require('merge-json-webpack-plugin');

module.exports = {
  plugins: [
    new MergeJsonPlugin({
      force: false,
      groups: [
        {
          files: [
            'common-manifest.json',
            'firefox-manifest.json'
          ],
          transform: (outputJson) => outputJson,
          to: 'manifest.json',
        },
        {
          pattern: '*.json', // glob. see https://github.com/mrmlnc/fast-glob
          to: 'merged-[contenthash].json',
        },
      ],
    }),
  ],
};

Options

• cwd[string] - The directory, an absolute path, for resolving files. Defaults to webpack context

• groups[array] - Files to merge and destination path

  • files[string[]] - Array of files, path resolved relative to cwd.
  • pattern[string[]] or [string] - [Fast-Glob] pattern matching. The order of merge is not guarenteed.
  • transform[function] - A function to modify the merged json contents. The return json value is written to the output file. If the function returns a promise, it will be awaited.
  • to[string]: Destination path to write the files to.
  • globOptions[GlobOptions] - Options to foward to fast-glob when glob is used otherwise ignored. See https://github.com/mrmlnc/fast-glob#options-3.

• minify[boolean] - Minify the output json. Enabled by default in production mode.

• mergeFn[function] - A function used to merge two objects. Defaults to Object.assign.

// webpack.config.js
const MergeJsonPlugin = require('merge-json-webpack-plugin');
const _ = require('loadsh');

const customizer = (objValue, srcValue) => {
  if (_.isArray(objValue)) {
    return objValue.concat(srcValue);
  }
};

const merge = (object, other) => {
  return _.mergeWith(object, other, customizer);
};

module.exports = {
  plugins: [
    new MergeJsonPlugin({
      mergeFn: merge,
    }),
    new MergeJsonPlugin({
      mergeFn: (prev, current) => Object.assign(prev, current),
    }),
  ],
};

• force[boolean] - Overwrites files already in compilation.assets (usually added by other plugins/loaders). Disabled by default.

• globOptions[GlobOptions] - Options to foward to fast-glob when glob is used otherwise ignored. See https://github.com/mrmlnc/fast-glob#options-3.

Changelog

v6.2.1 (2025-07-06)

Bug Fixes

• fix ignore pattern glob for json (6ffaca5)